1. Field of the Invention
This invention relates generally to devices and methods for the liquid separation of materials based upon differences in specific gravity. Particularly, the invention relates to an apparatus and method for the liquid separation of edible products from unedible portions thereof. Even more specifically, it relates to a liquid separation system for the treatment of raisins, wherein the edible fruit or raisin, is separated from the unedible portion which includes: stems, cap stems, waterberries, mold, and other waste.
2. Prior Art Statement
In the production of raisins, grapes are harvested from the vineyards in bunches and then dried to a moisture content of about 20%. These bunches of dried grapes include waste materials, such as, for example, the dried vines, stems, mold, and the like. The product is then transported to storage areas where it is fumigated and dried until the fruit has a moisture content of approximately 14%. The storage areas are generally fabricated of wood, and therefore, the waste materials further include wood particles which become matted into the fruit. The grapes are then processed in a series of mechanical operations designed to separate the fruit from a majority of the waste materials utilizing tumblers, rollers, water baths, etc. The product is then passed through a fluming station and thereafter, ready to be finally treated to produce a product suitable for commercialization.
In processing the edible and unedible materials, as above, it has been customary to employ laborers to remove such waste materials from the finally processed raisin. A number of hand sorters remove the unedible materials as the fruit and waste materials are transported as for example, by shaker screens, conveyors, and the like. Hand sorting, today, has become unfeasible due to prohibitive labor expenses and more exacting standards, including more stringent specifications as to the content of fruit sold to consumers (where only several parts per thousand waste in the commercial product is permitted). Moreover, the present production techniques which utilize high velocity air currents followed by water baths do not produce commercially acceptable raisins. It has therefore become increasingly important to develop improved mechanical devices to perform the above type separation in a more efficient and economical manner.
While some of the prior art is directed to the general principle of separating edible portions of fruit from unedible portions and other waste materials, it is in large part directed to separation by means of mechanical abrasion between concentric tubular members, interacting fruit between tubular members or rolls, or utilizing fan blades and the like to impel the raisins into a wall, against other raisins, or into baffles, screens, and the like.
The general principle of floation separation of frost damaged citrus fruit from undamaged citrus fruit is known. See for example: U.S. Pat. No. 994,654--issued to Parker and U.S. Pat. No. 2,283,512--issued to Sias.
U.S. Pat. No. 2,152,143, issued to Martin, is directed to sluicing raisins through a riffled structure of a hydraulic separator where stones and heavier particles (including raisins) drop out and fragments, such as cap stems, float toward the top of a water bath.
U.S. Pat. No. 1,269,966, issued to Shepard is directed to the treatment of raisins by immersing same in a body of water which is agitated by a worm gear, the latter of which mechanically interacts with the raisins to dislodge the cap stems. The raisins and heavier foreign materials are conveyed by the worm gear through a section of the tank where the heavier materials are pumped out and into a second stage of the apparatus for further treatment utilizing an agitating screen and pressurized fluid sprays. This process ultimately relies upon a screening process for the final separation of the fruit from the waste materials.
In U.S. Pat. No. 1,754,923, issued to Weigand, a liquid separation technique is utilized to separate prunes into various qualities and grades by progressively subjecting them to more dense solutions.
The prior art does not provide a suitable apparatus and method for the liquid separation of materials which is highly efficient and economical and which is compatible with present processing techniques and may be incorporated "in-line" to treat commercial quantities of materials. Moreover, the known prior art techniques have been proven to be unacceptable in the separation of raisins from stems, cap stems, waterberries, mold, wood chips, and other waste.
Accordingly, an apparatus and method is needed to meet todays standards in providing commercial quantities, of product free of mold, substandards, and other unedible waste materials. The present invention fills such a need by providing a means to treat and process free flowing raisins at acceptable standards and at feed rates incurred in production type "in-line" processes. Bulk materials are thrust into a solution of predetermined density and then reacted with an issuing stream of solution which combines to separate the materials. Conveyors are provided to transport the respective constituents, above, from the receptacle for disposal or further treatment. The present invention comtemplates the separation of various materials utilizing specific gravity differentials, and is specifically directed to the separation of edible materials from unedible materials including waste. While the invention is specifically described with reference to the processing of raisins, it is to be understood that the apparatus and principles relative thereto can equally be applied to promote separation of various types of materials including, for example, the separation of poultry from bones and gristle, green beans from stems and leaves, peas from pods and stems, and the like.